A mainframe computer system may be configured to run multiple operating systems. A logical segmentation of a mainframe's memory and other resources that allow the logical segmentation to run its own copy of an operating system and associated applications is called a Logical Partition (LPAR). LPARs are created by special hardware circuits and allow multiple system images to run in one machine. This may be multiple instances of the same operating system or different operating systems. With respect to systems designed by International Business Machines Corporation (“IBM”), this is known as a “virtualized System/390 processor complex.” LPARs are implemented in hardware extensions. IBM's PR/SM (“prism”), Hitachi's MLPF and Amdahl's MDF are examples of LPARs. MDF was the first to provide hardware that was the equivalent of IBM's virtual machine (VM) operating system, which supports multiple system images in software. Interestingly enough, an LPAR can host VM, which itself can host multiple operating systems.
In a dynamic LPAR system, a device currently assigned to an LPAR ‘A’ may be dynamically reassigned to another LPAR ‘B’. When this happens, the resource configuration database (Object Data Manager for that LPAR) will indicate that the device is missing from LPAR ‘A’. There is considerable system overhead associated with removing a previously assigned resource from the LPAR as opposed to just indicating that it is missing. Also, the resource may later be again reassigned back to the LPAR to which it was originally assigned and considerable overhead would again be expended in recreating objects for the resource. If the resource has “children” attached, those children will also be listed as missing. For example, if the resource is an asynchronous adapter (parent) the adapter also has a number of ports (children) that also have to be listed as missing if the parent is listed as missing.
While indicating that a previously assigned resource is missing if it is reassigned is a simple way to handle this problem, the Advanced Interactive Executive (AIX) diagnostic subsystem normally treats a resource that is missing as potentially being caused by a hardware problem which would result in an unnecessary service call in the instance of a reassigned resource. AIX is IBM Corporation's version of the UNIX operating system.
There is, therefore, a need for a method for managing dynamically reassignment of LPARs to prevent unneeded service calls without having to change the architecture of missing resource resolution or incurring high system overhead by removing the resource if it is reassigned.